Abstract
The study evaluated the efficacy of methanolic extracts of Ruta chalepensis L. (Rutaceae), Withania somnifera (L.) Dunal (Solanaceae), Cleome paradoxa (B. Br.) (Capparaceae) and Heliotropium longiflorum (Hochst & Steud. ex A. DC.) Jaub.& Spach (Boraginaceae) aerial parts against Culex pipiens larvae. Different concentrations (100-500ppm) of the methanolic extracts of the plants were tested towards larval mortality and development of C. pipiens separately. Larval mortalities were counted at 2, 4 and 10 days after treatment. Egg hatchability was determined at 4 and 7 days after treatment. Percentage of successful pupation and adult emergence were determined by monitoring on daily basis until all adults in the control had emerged. All plants extracts exhibited variable activities. The greatest effect was with R. chalepensis which showed acute (2 days) and chronic (10 days) LC50 of 132.6 & 96.56 ppm, respectively. Larval mortality up to 84.47% & 85.53%, were observed with C. paradoxa and R. Chalepensis respectively. Egg hatch was significantly reduced about equal with R. chalepensis and W. somnifera extracts. Concentration levels of C. paradoxa (>= 200 ppm) and H. longiflorum (>= 400ppm) showed significant hindrance to the larval development and reduction to resulting pupae and adults. Drastic development retardation was shown with extract of C. paradoxa leaves (300ppm), but only 15.3% & 5.6% of larvae reach pupal and adult stages respectively. The larvicidal activity of methanolic extracts of R. chalepensis, W. somnifera, C. paradoxa, H. longiflorum proved to be effective against C. pipiens larvae.